1. Field of the Invention
The present invention relates to a cogeneration apparatus utilizing an internal combustion engine, and particularly to an engine cogeneration system suitably for placing on a residence to supply both electric power and heat for use in a household.
2. Description of the Related Arts
Conventionally, a so-called cogeneration system has been known in which a power generator is driven by an engine (internal combustion engine) utilizing gasoline or municipal gas as fuel to obtain electric power from the power generator and at the same time, exhaust heat from the engine is recovered to be utilized as a heat source. In recent years, a system in which the cogeneration apparatus is placed on a residence to obtain both electric power and heat consumed in the household therefrom, i.e., the engine cogeneration system has been made attracted from the viewpoint of saving energy.
The conventional techniques have been known for example in Japanese Patent Laid-Open Publication No. 2003-134674 that cogeneration apparatuses are placed on a plurality of households, these apparatus are connected to make a network, the variation in power load in each household is dealt with increasing or decreasing driving generators within the network.
In the conventional techniques, no consideration is made to make a network for heat demand, and have a problem in terms of controlling both of heat demands and power demands in each household to follow their variation in each household.
Specifically, in conventional techniques, since network for heat demand is not constructed, the driving of the power generator in each household is to be controlled irreverent to the heat demand in the household, resulting in the problem in terns of control due to making it difficult to follow in both load variations of the heat demand and power demand in an appropriate manner.
Here, how the power demand and heat demand are changed within one day (24 hours) in each of seasons will be described. FIG. 11 shows power load [KW] measured at an interval of 30 minutes in each season (summer, spring and winter) over 1 day (24 hours), and FIG. 12 shows heat load [KJ/s] measured at an interval of 30 minutes in each season (summer, spring and autumn) over 1 day (24 hours).
As is clear from FIG. 11 and FIG. 12, it can be understood that both the power generation and heat generation are greatly varied within one day, and particularly, in the case of the heat, it is varied 10 times or more at the maximum. The variations also depend upon the seasons, and there is difference of 10 times or more in winter and summer.
A ratio of the power load to the heat load is calculated from FIG. 11 and FIG. 12, and is shown in FIG. 13 as a heat/power ratio, and FIG. 14 shows a total load adding the heat load to the power load. Is has, of course, be proven that they are greatly varied in the time zone and the seasons.
Consequently, in the cogeneration systems in the conventional techniques, it is difficult to follow the variation both in the power load and the heat load, and at this time, in the conventional techniques, the power source is driven to meet the heat load. This results in surplus power or power shortage, this in turn increase the period for conducting reverse current or power interchange within the cooperative systems, and reduces the economical merit obtainable by the cogeneration.
An object of the present invention is, therefore, to provide an engine cogeneration system, which makes it possible to follow variations both in the heat demand and power demand in an effective manner.